(Reuters) - Catalyst Pharmaceuticals Inc, rebuked by U.S. Senator Bernie Sanders for its high drug prices, on Thursday defended its $375,000 treatment for a rare disease, saying the price was in line with similar products in the industry.

Sanders, a vocal critic of high drug prices, had written to Florida-based Catalyst earlier this month, asking it to justify its price for Firdapse, a medication for a rare neuromuscular disease that affects about one in 100,000 people in the United States.

Drug pricing has been a major talking point in the US for the past few years. It was also one of the campaign promises made by President Donald Trump in the 2016 elections. However, healthcare costs have not gone down significantly.

Last month, the Trump administration proposed a rule to overhaul the industry's system of rebates, or discounts, while Sanders unveiled legislation aimed at lowering drug prices.

For years, patients were able to get Firdapse for free from Jacobus Pharmaceuticals, a small New Jersey-based drug company that offered the drug through a U.S. Food and Drug Administration (FDA) program called Compassionate Use.

The program allows patients with rare diseases and conditions access to drugs not yet approved outside of a clinical trial, when there is no viable alternative.

Catalyst bought the U.S. rights to the drug in 2012 and got approval to sell it in the US in November last year.

Sanders said in a statement provided to Reuters on Thursday that Catalyst had shown a "blatant disregard for patients with LEMS (Lambert-Eaton Myasthenic Syndrome)" who he said were already rationing their medication because of the high price-tag.

"I will ask FDA Commissioner Gottlieb to act immediately to help patients who are suffering," said Sanders, who is seeking the Democratic Party's presidential nomination in 2020.

The company said, before its November approval, only about 200 of an estimated 3,000 LEMS patients in the US received some form of Firdapse, pointing to a large unmet medical need.

"Now, for the first time, LEMS patients have confidence their therapy is FDA approved and is safe and effective," Catalyst's Chief Executive Officer Patrick McEnany said in a letter (https://bit.ly/2NkmIRU).

The company said that Firdapse's price was similar to other medicines that provide a significant clinical benefit in treating ultra-rare diseases, adding it believed the drug would be widely reimbursed by insurers for the small population it treats.

(Reporting by Manas Mishra and Aakash Jagadeesh Babu in Bengaluru and Yasmeen Abutaleb in Washington; Editing by Arun Koyyur and Sweta Singh)